The Pelton hydroelectric project was completed in 1958, Pelton Dam’s concrete structure rises 204 feet from bedrock. The dam is 26-1/2 feet thick at its base, tapering to 8 feet at the top. Width of the dam is 965 feet. Three generators produce enough electricity to power more than 45,000 homes.
A small regulating dam was constructed 2.4 miles downstream from Pelton. The reservoir behind the dam allows PGE to control the river flow to maintain favorable biological conditions for aquatic life in the 100-mile stretch of the lower Deschutes. The Confederated Tribes of the Warm Springs Reservation installed a turbine unit at the regulating dam in 1982. It generates enough electricity to power more than 7,000 homes. PGE operates this facility remotely from the Pelton Round Butte Control Room.
Round Butte hydroelectric project, completed in 1964, is the largest hydroelectric dam wholly within the state of Oregon. The massive 1,380-foot-long rock-fill structure rises 440 feet from its bedrock foundation. It is about 2,500 feet thick at its base and 44 feet thick at the crest. Round Butte’s three generators produce enough electricity to power more than 96,500 homes.
The original fish-passage facilities included a three-mile-long fish ladder between the Pelton Regulating Dam and Pelton Dam. A cable tramway system also was constructed to lift large adult fish over the 440-foot-high Round Butte Dam. Unfortunately, the downstream fish-passage system failed, so the ladder for upstream passage is not in use.
In July 2004, a historic agreement paved the way for salmon and steelhead to again migrate past Pelton Round Butte’s three dams for the first time since 1968. The downstream fish passage problem was created in large part by the currents in Lake Billy Chinook swirling in eddies with no particular direction. Juvenile salmon and steelhead rarely found their way toward the Pacific.
The solution is that PGE will build a 270-foot underwater tower rising from the lake bottom behind Round Butte Dam, at a cost of $60 million. A large disc at the top of the tower will draw in most of the surface water, altering the current to attract fish. Fish will be screened at the intake and trucked downstream of the dams for release on their journey to the Pacific.
Reintroduction of salmon and steelhead above the project is planned to occur in 2007. The completion of the water tower with downstream fish passage is scheduled for 2008. Adult fish should return above the project in 2010. The improvements will potentially reopen a new fish passage area of 226 stream miles to salmon and steelhead migration.
Under a new project relicensing agreement, PGE and the Confederated Tribes of the Warm Springs Reservation will invest more than $121 million over the next 50 years for fish-related work in the Deschutes.
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